Bottom Line:
In contrast, controls treated with native MCP-1 had enhanced arthritis symptoms, indicating that the inhibitory effect is specific to the antagonist.In experiments where the antagonist was given only after the disease had already developed, there was a marked reduction in symptoms and histopathology, although individuals varied in the magnitude of the response.The mechanism of inhibition of disease is not known, although the results suggest that it could be more complex than the competitive inhibition of ligand binding that is observed in vitro.

Affiliation: Biomedical Research Centre and Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.

ABSTRACTAn antagonist of human monocyte chemoattractant protein (MCP)-1, which consists of MCP-1(9-76), had previously been characterized and shown to inhibit MCP-1 activity in vitro. To test the hypothesis that, by inhibiting endogenous MCP-1, the antagonist has antiinflammatory activity in vivo, we examined its effect in the MRL-lpr mouse model of arthritis. This strain spontaneously develops a chronic inflammatory arthritis that is similar to human rheumatoid arthritis. Daily injection of the antagonist, MCP-1(9-76), prevented the onset of arthritis as monitored by measuring joint swelling and by histopathological evaluation of the joints. In contrast, controls treated with native MCP-1 had enhanced arthritis symptoms, indicating that the inhibitory effect is specific to the antagonist. In experiments where the antagonist was given only after the disease had already developed, there was a marked reduction in symptoms and histopathology, although individuals varied in the magnitude of the response. The mechanism of inhibition of disease is not known, although the results suggest that it could be more complex than the competitive inhibition of ligand binding that is observed in vitro. The demonstration of the beneficial effects of an MCP-1 antagonist in arthritis suggests that chemokine receptor antagonists could have therapeutic application in inflammatory diseases.

Figure 5: The effect of treatment with MCP-1 antagonist after disease onset. Animals were injected with CFA once at day 0 and examined daily for the visual appearance of erythema and swelling around the joints as measured with a micrometer. 23 of 40 mice developed swelling at different times, and they were injected daily with 2.0 mg/kg of either the MCP-1 antagonist or the MCP-1Ala control, on the day indicated by the arrows, until day 28. (a) The swelling measurements of three representative examples from the 13 controls (•, ○, ◫̶ ). (b) Three representative examples from the 10 antagonist-treated mice (▴, ▵, X).

Mentions:
Although the experiments described so far demonstrate that the MCP-1 antagonist is capable of preventing the onset of arthritis, they do not show whether the antagonist inhibits disease that is already evident. The postonset situation is a much more stringent test of the ability of the antagonist to inhibit disease, as cell infiltration and inflammatory events are already going on when the antagonist treatment is started (12). Another reason to address the postonset effects is that this more closely reflects the clinical situation where symptoms are already apparent when a patient presents with RA. To test the effects of the antagonist on existing disease, we primed the mice at day 0, but then delayed treatment until after significant swelling was apparent. The results for representative individuals from the control peptide– (Fig. 5 a), and antagonist- (Fig. 5 b) treated groups are shown. The individuals from the control group generally had recurrent swelling after symptoms first became apparent. This is typical of the disease in this model. Individuals from the treated group showed an immediate reduction of swelling and duration of inflammatory episodes. Some degree of relapse of the antagonist-treated animals was apparent at later time points, and the duration and persistence of this was highly variable. Nevertheless, when all the animals were taken into account (not shown), the results indicated that the antagonist greatly reduced the symptoms.

Figure 5: The effect of treatment with MCP-1 antagonist after disease onset. Animals were injected with CFA once at day 0 and examined daily for the visual appearance of erythema and swelling around the joints as measured with a micrometer. 23 of 40 mice developed swelling at different times, and they were injected daily with 2.0 mg/kg of either the MCP-1 antagonist or the MCP-1Ala control, on the day indicated by the arrows, until day 28. (a) The swelling measurements of three representative examples from the 13 controls (•, ○, ◫̶ ). (b) Three representative examples from the 10 antagonist-treated mice (▴, ▵, X).

Mentions:
Although the experiments described so far demonstrate that the MCP-1 antagonist is capable of preventing the onset of arthritis, they do not show whether the antagonist inhibits disease that is already evident. The postonset situation is a much more stringent test of the ability of the antagonist to inhibit disease, as cell infiltration and inflammatory events are already going on when the antagonist treatment is started (12). Another reason to address the postonset effects is that this more closely reflects the clinical situation where symptoms are already apparent when a patient presents with RA. To test the effects of the antagonist on existing disease, we primed the mice at day 0, but then delayed treatment until after significant swelling was apparent. The results for representative individuals from the control peptide– (Fig. 5 a), and antagonist- (Fig. 5 b) treated groups are shown. The individuals from the control group generally had recurrent swelling after symptoms first became apparent. This is typical of the disease in this model. Individuals from the treated group showed an immediate reduction of swelling and duration of inflammatory episodes. Some degree of relapse of the antagonist-treated animals was apparent at later time points, and the duration and persistence of this was highly variable. Nevertheless, when all the animals were taken into account (not shown), the results indicated that the antagonist greatly reduced the symptoms.

Bottom Line:
In contrast, controls treated with native MCP-1 had enhanced arthritis symptoms, indicating that the inhibitory effect is specific to the antagonist.In experiments where the antagonist was given only after the disease had already developed, there was a marked reduction in symptoms and histopathology, although individuals varied in the magnitude of the response.The mechanism of inhibition of disease is not known, although the results suggest that it could be more complex than the competitive inhibition of ligand binding that is observed in vitro.

Affiliation:
Biomedical Research Centre and Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.

ABSTRACTAn antagonist of human monocyte chemoattractant protein (MCP)-1, which consists of MCP-1(9-76), had previously been characterized and shown to inhibit MCP-1 activity in vitro. To test the hypothesis that, by inhibiting endogenous MCP-1, the antagonist has antiinflammatory activity in vivo, we examined its effect in the MRL-lpr mouse model of arthritis. This strain spontaneously develops a chronic inflammatory arthritis that is similar to human rheumatoid arthritis. Daily injection of the antagonist, MCP-1(9-76), prevented the onset of arthritis as monitored by measuring joint swelling and by histopathological evaluation of the joints. In contrast, controls treated with native MCP-1 had enhanced arthritis symptoms, indicating that the inhibitory effect is specific to the antagonist. In experiments where the antagonist was given only after the disease had already developed, there was a marked reduction in symptoms and histopathology, although individuals varied in the magnitude of the response. The mechanism of inhibition of disease is not known, although the results suggest that it could be more complex than the competitive inhibition of ligand binding that is observed in vitro. The demonstration of the beneficial effects of an MCP-1 antagonist in arthritis suggests that chemokine receptor antagonists could have therapeutic application in inflammatory diseases.